Albert Barnes Commentary Judges 7:8

"So the people took victuals in their hand, and their trumpets; and he sent all the men of Israel every man unto his tent, but retained the three hundred men: and the camp of Midian was beneath him in the valley." — Judges 7:8 (ASV)

The sense is, “And they (the three hundred) took the victuals and trumpets of the people (all the people of Judges 7:7) into their hands”; so that each of the three hundred should have a trumpet and a pitcher.